Apparatus for spray drying rubber latex and other solutions, dispersions, or emulsions



July so, 1935. M. J. STAM 2,009,531

APPARATUS FOR SPRAY DRYING RUBBER LATEX AND OTHER SOLUTIONS, DISPERSIONS OR EMULSIONS Filed July 12, 1954 Patented July 30, 1935 APPARATUS FOR SPRAY DRYING RUBBER I LATEX AND OTHER SOLUTIONS, DISPER- SIONS, R EMULSIONS Martinus Joinnes' Stam, The Hague, Netherlands Application July 12, 1934, Serial No. 734,880 In the Netherlands April 24, 1934 4 Claims. (Cl. 159-4) It is known to obtain rubber and other dissolved or dispersed solid substances in the form of a fine powder by spraying the solution or dispersion of these substances in a hot drying at 6 mosphere. A suitable apparatus for this purpose is described for instance in my co-pending application Serial No. 638,264, filed October 17th, 1932, in which the liquid is conducted from below through a vertical rotary tube with a trumpet- 10 shaped discharge member and is sprayed thereby in a substantially horizontal direction into a stream of drying gas which is conducted from below the spraying disk through an annular space between an outer chamber and an inner chamber, the latter having a fiat bottom and a conical top and being wholly surrounded by the former. Said stream of drying gas carries the spray towards the top of the outer chamber from which it is discharged into a separator. In this propelled by a propeller mounted on the tubular centrifugal element below the spraying device in an enlarged part of a downward extension of the aforesaid outer chamber.

In this apparatus the spraying requires a very high rotating speed of the centrifugal tube and the propeller for the drying gas makes the same number of revolutions. It has been found that this arrangement has some drawbacks. The propeller requires too much power so that this apparatus works ineconomically. Also it has been found very difficult to ensure that the gas current takes up all the sprayed particles before they touch the wall of the outer chamber because some of the particles are too heavy to be deflected suificiently from their path by the gas current. Such particles will stick to the walls and give rise to a narrowing of the passage for the drying gas and may lead to a gradual obstruction of the gas passage.

One object of the present invention is to provide an apparatus without these drawbacks. Another object is ,to provide an apparatus which will work economically and efliciently, without the possibility of particles sticking to the walls of a drying chamber, obstructed gas passages or insuflicient gas currents and by which the spray dried particles are carried away bya uniform gas current rising from the bottom of a drying chamber and carrying the dried particles to a discharge aperture in the top of the drying chamber from which they may be conducted into a separator. The spraying means are the same as in my older application and consist of a quickly revolving tube ending in a trumpet-shaped sprayapparatus the drying gas current is aspirated and.

ing device through which the liquid rises upwards in the form of a film against the inner wall of the tube, said film being disrupted in the trumpet-shaped end piece into an extremely great number of very small droplets which are ejected 5 in a substantially horizontal direction.

According to the invention this spraying device is arranged in a large drying chamber. The drying gas is exhausted from the top of said chamber and discharged with the sprayed particles into a separating device. A hot gas is introduced through the bottom ofthe. drying chamber. The chamber is sufflciently large to allow the sprayed particles to be deflected upwar'dly by the rising gas before striking the walls of the chamber, this being facilitated by the evaporation of. liquid from the drying droplets rendering them much lighter. I

The invention is illustrated by the accompanying drawing.

In the drawing l is the spraying device, pro- .vided inthe centre of the drying chamber 2, having a bottom 3 with a centralaperture round the spraying device 4 and apertures 5 uniformly distributed in a circle concentric with the spraying device. Below the bottom of the chamber is a space into which hot air is conducted from a heating device (not shown) entering into said space through the inlet a. This space is divided by partitions 6 into a plurality of conduits of substantially equal capacity for conducting hot drying gas to the bottom of the chamber. The conduits all discharge in the central aperture 4 and each in one of the apertures 5. The top of the drying chamber is conically shaped and in the centre above the spraying device is the discharge aperture I). The drying gas is aspirated through the whole apparatus by an exhauster (not shown) which preferably is provided at the end of the separator so that the drying gas with the dried particles discharged from the drying chamber are introduced intoa separator (not shown) in which the dried particles are collected and from which the gas is aspirated by the exhauster.

Instead of one ring of apertures 5 there may be applied several rings of apertures provided every conduit discharges into the same number of equal apertures, so as to cause a uniform gas current in the drying chamber.

In operating the apparatus a current of hot gas is aspirated through the apparatus. The liquid carrying the substance to be dried is introduced through the hollow shaft in the centre of the apparatus said shaft revolving with a high speed. Therefore, the liquid rises in the form of a thin film against the inner wall of said shaft and is discharged in the chamber in the form of a'flne mist of minute droplets. These droplets are dried and carried away in upward direction by 5 the current of hot drying gas in its path from the bottom to the discharge end of the drying chamber. The separation of the dried particles from the gas current is carried out in known manner. The subatmospheric pressure in the drying chamber promotes the evaporation. The centrifugal force by which the spray is ejected can be controlled easily and independent from the force of he drying gas current which latter can easily be regulated insuch manner that all the dry parti- I cles are carried away and complete drying is obtained without using unnecessary quantities of drying gas. The exhauster or air pump is advantageously protected by a filter to prevent the dried powder to enter it. Between this filter and the spraying chamber separator means are provided to collect the bulk of the dried particles before the gas current enters the filter.

It is very important-that the drying agent is distributed through the bottom of the chamber in such manner that the conditions of temperature and velocity are as uniform as possible in all sectors of the chamber. In that case the diameter of the drying chamber and the volume of drying gas are minimal.

What I claim is:- I

1. Apparatus for converting rubber latex and other solutions, dispersions and emulsions into a very fine powder, comprising a drying chamber having a large cylindrical portion and a conical top member, a tubular centrifugal element extending from the bottom centre of said chamber and ending in a trumpet-shaped spraying device which discharges in said chamber in a substantially horizontal direction, a central exhaust aperture in the top of said chamber, a space below the bottom of said chamber communicating with a source of hot drying gas, partitions in said space forming a plurality of conduits of substantially equal capacity and each discharging into a central annular space around the centrifugal tubular element and through at least one aperture in the bottom of said chamber, the apertures corresponding with each conduit being of substantially the same capacity and arranged in at least one circle concentric with the centrifugal tubular element.

2. Apparatus for converting rubber latex'and rubber solutions, dispersions and emulsions into a very fine powder, comprising a drying chamber, having atapering top chamber with a central exhaust aperture and a substantially closed bottom, a tubular centrifugal element, extending from the bottom center of the chamber and ending in a trumpet-shaped spraying device which discharges into said chamber in a substantially horizontal direction, a space below the bottom of said chamber communicating with a source of hot drying gas and a plurality of apertures in said bottom, symmetrically distributed in at least one circle concentric with the centrifugal tubular element and all discharging the drying gas in substantially vertically directed streams around the spraying device. a

3. Apparatus according to claim 2, in which there is a substantial distance between the apertures in the bottom and the side wall of the drying chamber.

4. Apparatus for converting rubber latex and other solutions, dispersions and emulsions into a very fine powder, comprising a drying chamber having a large cylindrical portion and a conical top member, a tubular centrifugal element ex- MARTINUS JOANNES STAM. 

